1.Field of the Invention
The present invention relates to a generator system utilizing a fuel cell and more particularly to a generator system utilizing a fuel cell capable of controlling the output of the fuel cell in response to an amount of energy variations in load.
2. Description of the Prior Art
The conventional generator system utilizing a fuel cell is in general designed and constructed to deliver a constant output as shown in FIGS. 1 or 2.
FIG. 1 shows a conventional generator system utilizing a fuel cell which is driven while a fuel cell is connected to a power supply of a system. The generator system utilizing a fuel cell shown in FIG. 1 comprises a raw material tank 1 for storing therein a material to be reformed; 2, a reformer adapted to produce a reformed gas by reforming the raw material fed from the raw material tank 1; 4, a fuel cell; 10, a DC/DC converter; 11, an inverter; 8A, a system power supply; 9, a load; 14B, a controller which is, for instance, in the form of a microprocessor and which controls all about the generator system utilizing a fuel cell; and 30 a generator system utilizing a fuel cell.
The output power P.sub.F derived from the fuel cell 4 is applied through the DC/DC converter 10 to the inverter 11 so that the DC power is converted into the AC power. The inverter output power P.sub.I ; that is, the fuel cell output P.sub.F is delivered to the load 9. In this case, the AC power P.sub.L delivered to the load 9 is equal to P.sub.I. As the load 9 is increased, the power supply must be increased accordingly, but when the output power P.sub.F delivered from the fuel cell is not sufficient, the power Ps from the power supply 8A must be combined with the output P.sub.I from the inverter 11 into the power P.sub.L which is supplied to the load 9. Therefore, the generator system utilizing a fuel cell is driven under the control of the controller 14B.
FIG. 2 shows a system consisting of the combination of a fuel cell and a battery, thereby supplying the power to the load. Reference numeral 1 represents a raw material tank; 2, a reformer; 4, a fuel cell; and 40 a generator system utilizing a fuel cell. The output P.sub.F derived from the fuel cell 4 is converted into a direct current by the DC/DC converter 10, whereby the DC/DC converter output power Pc.
The output Pc from the DC/DC converter 10 is constant and is delivered as the output P.sub.L and the output P.sub.B to the load 9 and the battery 8, respectively. It follows, therefore, when the value of the load 9 is light, an excess of the power P.sub.L delivered to the load 9 is supplied as the excess power P.sub.B to charge the battery 8. On the other hand, when the magnitude of the load 9 is heavy, the controller 14B operates in such a manner that in addition to the output power Pc from the DC/DC converter 10, the output power P.sub.B from the battery 8 is also delivered as the power P.sub.L to the load 9.
However, the above-described conventional generator systems utilizing a fuel cell have a common problem that it is extremely difficult to control the magnitude of the fuel cell output immediately in response to the variations in load.
This problem is caused by the characteristics of the reformer 2 shown in FIGS. 1 or 2. The reformer 2 evaporates a raw material to be reformed such as the mixture of water and methanol delivered from the raw material tank 1 and produces the hydrogen gas, which is a fuel, by a chemical reaction utilizing a reforming catalyst. The response time required for the reforming the raw material into the hydrogen gas in response to the instruction from the controller 14B is of the order of 0.5-2 minutes so that it is impossible to produce the required volume of the hydrogen gas within a time less than above. On the other hand, the response time of the load is of the order of microseconds, so that the response of the fuel cell output power P.sub.F lags behind in time with respect to the variations in load.
Then, in the case the generator system utilizing a fuel cell is driven, it is necessary to control the generator system utilizing a fuel cell by considering the response characteristic of the reformer 2 and the load 9.
Therefore, both the conventional generator systems utilizing a fuel cell have a problem that the output power delivered from the fuel cell to be applied to the load 9 cannot be controlled in response to the variations in load 9.